Choosing a Common IGP for the IP Internet
RFC 1371

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Network Working Group                                  P. Gross, Editor
Request for Comments: 1371                              IETF/IESG Chair
                                                           October 1992

              Choosing a "Common IGP" for the IP Internet
                 (The IESG's Recommendation to the IAB)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard.  Distribution of this memo is
   unlimited.

Special Note

   This document was originally prepared as an Internet Engineering
   Steering Group (IESG) recommendation to the Internet Architecture
   Board (IAB) in mid-summer 1991, reaching the current version by the
   date shown above.  Although the document is now somewhat dated (e.g.,
   CIDR and RIP II are not mentioned), the IESG felt it was important to
   publish this along with the recent OSPF Applicability Statement [11]
   to help establish context and motivation.

Abstract

   This memo presents motivation, rationale and other surrounding
   background information leading to the IESG's recommendation to the
   IAB for a single "common IGP" for the IP portions of the Internet.

   In this memo, the term "common IGP" is defined, the need for a common
   IGP is explained, the relation of this issue to other ongoing
   Internet Engineering Task Force (IETF) routing protocol development
   is provided, and the relation of this issue to the goal for multi-
   protocol integration in the Internet is explored.

   Finally, a specific IGP is recommended as the "common IGP" for IP
   portions of the Internet -- the Open Shortest Path First (OSPF)
   routing protocol.

   The goal of this recommendation is for all vendors of Internet IP
   routers to make OSPF available as one of the IGP's provided with
   their routers.

IESG                                                            [Page 1]
RFC 1371                Choosing a "Common IGP"             October 1992

Table of Contents

   1. Background ....................................................  2
   2. Multiple Internet Standard Routing Protocols Possible .........  3
   3. A Common IGP ..................................................  3
   4. Impact of Multi-protocol Topology and Integrated IP/CLNP Routing 3
   5. Commitment to Both IP and CLNP ................................  5
   6. Some History ..................................................  5
   7. IESG Recommendations ..........................................  6
   7.1 Regarding the Common IGP for the IP Internet .................  6
   7.2 Regarding Integrated IP/CLNP Routing .........................  7
   7.3 Limits of the Common IGP Recommendation ......................  7
   8. References ....................................................  8
   9. Security Considerations .......................................  9
   10. Author's Address .............................................  9

1. Background

   There is a pressing need for a high functionality non-proprietary
   "common" Interior Gateway Protocol (IGP) for the TCP/IP protocol
   family.  An IGP is the routing protocol used within a single
   administrative domain (commonly referred to as an "Autonomous System"
   (AS).

   By "common", we simply mean a protocol that is ubiquitously available
   from all router vendors (as in "in common").  Users and network
   operators have expressed a strong need for routers from different
   vendors to have the capablity to interoperate within an AS through
   use of a common IGP.

   Note:  Routing between AS's is handled by a different type of routing
   protocol, called an "Exterior Gateway Protocol" ("an EGP", of which
   the Border Gateway Protocol [2] and "The Exterior Gateway Protocol"
   [3] are examples.)  The issues of routing between AS's using "an" EGP
   is not considered in this memo.

   There are two IGPs in the Internet standards track capable of routing
   IP traffic -- Open Shortest Path First (OSPF) [4] and Integrated IS-
   IS [5] (based on the OSI IS-IS). These two protocols are both modern
   "link state" routing protocols, based on the Dijkstra algorithm.
   There has been substantial interaction and cooperation among the
   engineers involved in each effort, and the protocols share some
   similar features.

   However, there are a number of technical design differences.  Most
   noteably, OSPF has been designed solely for support of the Internet
   Protocol (IP), while Integrated IS-IS has been designed to support
   both IP and the OSI Connectionless Network Layer Protocol (CLNP)

IESG                                                            [Page 2]
RFC 1371                Choosing a "Common IGP"             October 1992

   simultaneously.

2. Multiple Internet Standard Routing Protocols Possible

   The Internet architecture makes a distinction between "Interior
   Gateway Protocols (IGPs)" and "Exterior Gateway Protocols (EGPs)".